The sport's most popular driver was one of many wrestling with the impact of Stewart's absence, but Earnhardt was firm about the circumstances of the injury and whether the moonlighting would have an impact on other drivers' extracurricular racing pursuits.

"Tony loves to race, and I think he should race as much as he wants," Earnhardt told USA TODAY Sports at Hendrick Motorsports headquarters, where he launched the team's new social media command center. "There's danger in racing. These types of things are going to happen.

"I think he can do whatever he wants to do. He's having fun living his life. You've got one life, man. You can't sit there and sit on the sidelines worrying about what's going to happen to you. You've got to get out there and do it. He's just doing what he enjoys. Everybody else understands the risk and reward, and it was worth it to him."

It's uncertain how many races Stewart, 42, will miss after surgery for a broken tibia and fibula. He remained hospitalized Tuesday while awaiting a second surgery and will be replaced by Max Papis in the No. 14 Chevrolet on Sunday at Watkins Glen International.

Steven Meier, orthopedic surgeon and founder of Meier Orthopedic Sports Medicine of Beverly Hills who has not seen or treated Stewart, wrote in an e-mail to USA TODAY Sports that Stewart could be out for months to allow the bones to heal.

"Tibia fractures are known to take a long time to heal, usually three to four months just for the bone itself to heal," Meier wrote. "Then there is the process of rebuilding muscle strength through rehabilitation. However, if the bones are rigidly fixed with a rod, Tony could be getting back into a race car much sooner than that depending on how extensive the soft tissue injury was, whether infection becomes an issue and how long the soft tissue envelope takes to heal. So, conceivably, it is possible he could get back behind the wheel before the season ends."

The 10-race, 12-driver Chase for the Sprint Cup concludes Nov. 17. For Stewart, who is 11th in the standings, it effectively ended Monday night.

His injury again has raised questions about how NASCAR teams grant permission to Cup drivers who race outside the series.

While Stewart's role as co-owner of Stewart-Haas Racing permits him to race to his heart's content, he wasn't granted such leeway when he was employed by Joe Gibbs Racing, and many other teams frown upon their drivers putting their primary livelihoods at stake by competing in lower-tier series that inherently have lower safety standards.

Hendrick Motorsports President Marshall Carlson said there were no stipulations in the team's contracts that precluded moonlighting but there was a process for gaining consent for racing outside Cup.

"If they want to race anything other than with us, we have to have a conversation about it," Carlson told USA TODAY Sports. "We make sure there aren't any sponsor conflicts, scheduling conflicts or safety concerns."

Hendrick has supported Jeff Gordon and Jimmie Johnson driving in the International Race of Champions all-star series and also allowed Kasey Kahne to race sprint cars. But its four drivers aren't nearly as active in other series as Stewart, who competed in 90 races last year and was scheduled for more than 100 in 2013.

"I don't know that a list of prohibited activities makes a lot of sense," Carlson said. "You can't be Draconian about it. But if you want to learn how to do skydiving from outer space, do that after you retire. All that being said, guys break their legs walking around in parking lots in the winter. We have a program that seems to work, and the guys are really super conscious of the fact there is a lot riding on them."

Next-generation voice

Stewart is a budding icon of American motor sports who owns multiple racetracks and teams, so much is riding on his return.

Since becoming a Sprint Cup co-owner with Gene Haas four years ago, he has earned a seat at the table in long-term strategy and decision-making for the sport. When NASCAR elected to run a national series race on a dirt track for the first time in more than 40 years, Eldora Speedway was chosen largely because it was owned by Stewart.

With many living legends of racing, such as A.J. Foyt and Roger Penske, well into their 70s, the leadership of the next generation will come from multifaceted talents such as Stewart, who believes one of the best ways to be a racing evangelist is by barnstorming around the country's tiny dirt tracks and spreading the gospel via the grass roots. Therein lies more risk.

Stewart's wreck Monday night was his third in three weeks, but the Columbus, Ind., native has vehemently defended his decision to moonlight. In June, after friend and NASCAR driver Jason Leffler, 37, died after a sprint car crash in New Jersey, Stewart said: "I am as careful as I am when I get in a car on a city street. ... It's just part of it, and I am one of those that believe when it's your time it's your time."

Stewart, who also owns USAC and World of Outlaws teams, defended short track venues, saying, "There are facilities that need some work, and there are facilities that put a lot of effort into it. There are always things you can do better. ... Promoters are doing everything they can do to keep having tracks for drivers that want to be NASCAR drivers."

Last month, Stewart started a pileup that left 19-year-old Alysha Ruggles with a back injury at a track in upstate New York. He later flipped his sprint car five times in Ontario. When questioned about the flips, he told media: "That was not a big deal. I guarantee you there were 15 to 20 guys across the country that flipped just like that this weekend and were just fine just like we were. If it's bad, we will let you guys know."

Now, Stewart is faced with the probability of a long time out of racing at any level.

Earnhardt thinks his good friend will return at full speed just as past racing legends have.

"Tony's really tough," Earnhardt said. "He really reminds me a lot of A.J. Foyt and how A.J. always stood his ground. I perceive Tony as the same guy. He's just a different generation, but it's the same attitude.

"I admire him. Down in there, he's got a good heart. As brash and hard core as he is, he's got a real good heart for people and treats people good. You just hate to see those things happen to those kind of people. But he'll get tuned up and they'll sort him out, and he'll be back and it'll be forgotten. But it just sucks that he has to go through it. He's just doing something he really enjoys to do."

Leading even if not driving

While Stewart's return behind the wheel is indefinite, his role with Stewart-Haas Racing likely will keep him in the forefront of major issues in NASCAR.

"I think we won't miss the leadership because he'll still be there and definitely be as vocal," Earnhardt said. "I'll be aware of his presence even if he's not in the race car."

Stewart's streak of Sprint Cup starts dates to the 1999 Daytona 500 - his first career Cup race. He ranked 10th all time and was third among active drivers behind Jeff Gordon (710) and Jeff Burton (613).

He joins Denny Hamlin as Sprint Cup drivers who will miss races because of injuries this season. Hamlin broke his back in a crash at Auto Club Speedway in March and missed four races and part of a fifth.

After missing two races last year with a concussion, Earnhardt can relate to the frustration of sitting out, though he was more concerned with Stewart's recovery.

"You hate seeing people having to go through adversity and have to deal with the pain," he said. "I'm sure he's in a tremendous amount of pain and is going to have a tough road to get back on his rehab.

"It just sucks. Trying to overcome an injury is a real challenge, especially for athletes, and having to miss the races is going to be tough. The physical part is what you think about."